How to make (focused on modeling) burnt wood
You can create a burnt wood look by sculpting. Disclaimer: I am not very good at sculpting

Here is how I did it:

First add a cube and scale it to the dimensions of the wood plank.

Add enough edge loops so that all polygons look square


Subdivide the mesh in edit mode to a point where the square are about the size of the detail you want.


Add a displacement modifier.


Switch to sculpt mode and use the clay stripes brush


Repeat until happy.